Fixing an Engine Stop Switch for $0.30 (kill switch

Hello all,

I want to share with you how I repaired a faulty engine stop switch. The switch would not fully engage and sometimes would rattle and cut the motor. Please note that this is only what I did and I am not responsible for your outcome of following these instructions. In fact I encourage you to not follow these instructions at all and have all work performed by a Qualified Yamaha Service Center. If you do follow these steps it’s at your own risk.

What you’ll need:

  • Phillips Head Screw Driver
  • Small flat head screw driver (or something to pry with)
  • "clicky" pen
  • dikes


  1. Remove the phiilps screws from the bottom of the handlebar switch (I believe there are 3 or 4)
  2. Pull the two halves apart gently and remove the screw inside holding the engine stop switch into the handlebar switch assembly
  3. Remove the stop switch assembly (it should have a rectangle box with a contact that the button attaches too and a "bullet" that protrudes into grooves on the casing
  4. Once you have the stop switch removed you’ll notice a metal contact on the back that has a spring under it. This spring gets weak and no longer holds the switch into the proper connected state.
  5. Remove the metal contact carefully, be patient and delicate so as not to break the plastic or the metal clips holding the contact in place. Use a small flat head screwdriver or similar device to separate this part.
  6. Now there is a spring with a bullet on the other end. Remove this spring and bullet, clean the cylinder that the bullet goes into and the bullet so it can slide smoothly in the cylinder. Remove the spring from the bullet as close to the bullet as possible if it hasn’t already fallen off
  7. Now take the pen from earlier and remove the spring from it, insert the spring into the cylinder. If the diameter is too big you’ll need a smaller pen.
  8. Now for some trial and error, you’ll need to cut the spring from the pen so that it isn’t too long, however leave enough that the bullet fully engages the grooves. The pen I used I ended up using about 1/2 the spring and I have a really "stiff" switch now. I ended up with a spring about 2.5 times the depth of the cylinder with the bullet installed.
  9. Insert the bullet and new spring into the cylinder (discard the old spring) and compress the new spring with the back contact and hold everything together.
  10. Insert this assembly into your handlebar switch, you’ll have to move the contact and bullet in to get it into place. Just go easy and you’ll figure it out.
  11. Before putting the screw back in, hold it firmly in place with your thumb and test that the switch is able to be toggled easily and fully engages. To test that it is engaging remove your seat and turn the key on. As you move the switch you can hear the relay under the seat engaging and disengaging. Make sure that once it’s engaged, that wiggling the switch does not disengage it again.
  12. If it doesn’t engage properly, the spring is too short. If the switch is too hard to move, the spring is too long.
  13. Put everything back together.

If anyone is interested in what I did and these instructions are confusing, I am more than happy to take mine back apart and snap pictures of the process.